DE767855C - Process for the catalytic conversion of aliphatic hydrocarbons into cyclic compounds - Google Patents

Description

Process for the catalytic conversion of aliphatic hydrocarbons in cyclic compounds The invention relates to a method for catalytic Conversion of paraffinic or olefinic hydrocarbons with more than g and at most about 12 carbon atoms in cyclic compounds, for example the production of toluene from n-heptane or n-heptene, the treatment of paraffinic or olefinic gasolines for the purpose of obtaining gasoline with a higher octane number, etc.

It has been found that in the aforementioned reaction catalysts, which aluminum oxide and chromium oxide with a large active surface, which from their Hydroxides obtained by precipitation were produced in a special ratio and also contain alkali compounds to achieve particularly favorable results allow, especially with regard to a very large conversion capacity and a long service life. The best results are obtained with catalysts in which aluminum oxide and chromium oxide in a molecular ratio of (zo to 40): (go to 6o) are included. It was also found that the reaction temperatures should be between about 400 and 600 °.

The presence of alkali compounds in the present process The catalysts used improve the effectiveness of the aluminum oxide-chromium oxide catalysts essential. The alkali compounds can be used in various forms, z. B. in the form of alkali metal hydroxides, alkali metal carbonates, alkali metal sulfates, alkali metal phosphates and the like. The alkali hydroxides, carbonates and nitrates have themselves proved to be particularly suitable. On the other hand, alkali halides should be preferred should not be used as they will give less favorable results. It should, however no more than about 3o, preferably on 100 molecules of aluminum oxide-chromium oxide mixture ij to 20 atoms of alkali metal (Li, Na, K, Rb or Cs) must be present.

So was z. B. in the conversion of heptane into cyclic compounds at 465 = by means of various amounts of potassium nitrate in a catalyst which consisted of 30 mole percent A1., 0, and 70 mole percent Cr., 0 , found that the increase in the number of potassium atoms first led to a rapid increase in the amount of heptane converted into aromatics, the highest yield being found with an amount of potassium nitrate corresponding to about 15 to 20 K atoms per 100 mol of the oxide mixture. Further addition of galium nitrate caused the yield to drop rapidly. Example i n-heptane was produced at a rate of 10 ccm (6.8 g) per hour at = .16j- under atmospheric pressure .above -iS ccm- (16.1-) of a mixture of 30 llol percent ALO, and 7o JIoI- percent Cr, 03, which was pressed into lozenges of about 5 mm and to which 18 atoms of potassium (in the form of potassium nitrate) were added for every 100 molecules of oxide mixture. The average yield, measured in a working time of 4.6 hours, was 31 percent by weight of aromatic hydrocarbons, consisting essentially of toluene.

All other things being equal, but in the absence of potassium it was an average yield of 22.5 percent by weight aromatic carbons,% hydrocarbonsa which consisted mainly of toluene. Example 2 n-Nonane was with a rate of 20 cc (i4.35 g) per hour at .165 and atmospheric pressure over 40 ccm (37 g) of a mixture of 3o mol percent Ah03 and 70 MOI percent Cr .., 03, that pressed into lozenges of about 5 mm "-ar and 18 atoms of potassium (added during the production in the form of -, - contained potassium hydroxide) for every 100 g of oxide mixture, directed.

The reaction product obtained after 10 hours, which was liquid at ordinary temperature, represented 83 percent by weight of the starting material; 71: weight percent of product was aromatics, f; Weight percent olefins and 23 weight percent paraffins. The aromatics consisted of about 80 percent by weight of ortho-ethylethylbenzene and about 20 percent by weight of aromatics with fewer than 9 carbon atoms. In addition to a large amount of hydrogen, the gaseous reaction products contained small amounts of methane and ethane.

The method according to the invention can be performed under normal, reduced or elevated pressure (up to about 10 atmospheres).

It must also be noted that the contact times with the catalytic converter should not be chosen too short, otherwise olefins will be formed at the expense of aromatics will.

So z. B. at temperatures between 450 and 500- the contact time for the formation of aromatics a few seconds, z. B. more than 5 seconds. If, however, the conversion into cychsche compounds is to be carried out at more elevated temperatures, e.g. B. between 520 and 600 'and in the presence of hydrogen (for example, 5 to 10 Mo1 hydrogen on 1 Hol starting material), the pressure being 5 atmospheres, the contact time can be significantly shortened, for example to about 0.5 seconds.

If the hydrocarbon material is used to carry out the reaction Formation of cyclic compounds is recycled, it is advantageous to after passing over the catalyst, any higher-boiling substances from the reaction product to remove, since it has been found that this measure is an extension the life of the catalytic converter.

Claims (1)

PATENT CLAIM: Process for the catalytic conversion of aliphatic Hydrocarbons with more than 5 and at most about 12 carbon atoms in cy clic compounds using chromium oxide-aluminum oxide catalysts Temperatures above 400 @, characterized in that the hydrocarbons in contact with a catalyst at temperatures between about 400 and about 600 ° brings, the aluminum oxide and chromium oxide with a large active surface, which from their hydroxides obtained by precipitation were produced in a molecular ratio from (io to 40): (go to 6o) and also an alkali content of up to 30, preferably 15 to 20 atoms of alkali metal per 100 molecules of aluminum oxide and chromium oxide having. To distinguish the subject matter of the invention from the state of the art, im The following pamphlets were considered for the granting procedure «-Order of French Patent documents No. 827 002, 838010, Russian patent No. 46 gis.